Set Operation

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The Set Operation menu item is used to perform standard set operations on closed geometry objects (grids, meshes, and polygons). The result of this operation is always one or more polygons, unless the operation generates no output at all; for example, the intersection of two non-overlapping polygons would generate an empty polygon.


If the set operation generates more than one polygon, the output will be placed in a new folder.


Select the objects to be used for input from the Subject List and the Clip List.


Set Operation


Select the desired set operation here.


Difference:This option subtracts the area of the clip list from the areas defined in the subject list.


Intersection:This option generates the intersection of the combined area of the subject list with the combined area of the clip list.


Union:This option combines the areas of all objects defined in the subject list and the clip list.


Exclusive Or:This option generates the area NOT intersected by the subject list and the clip list.


Z Values


Any set operation could generate new data points. Use this setting to determine how their elevations are calculated.


Set to (value):This option assigns the value given as an elevation to any new data points that are created as a result of the set operation.


Interpolate:This option generates elevations for any new data points created as a result of the set operation, by linearly interpolating between existing points.


Extra Points


The output polygons from a set operation can be simplified based on their geometry; for example, the line (0,0), (0,2), (0,4) does not need to keep (0,2) because the two segments are parallel and share a common point.


Keep:Use this option to keep extra data points in the output geometry. This is often required for modeling to ensure consistent meshes between adjacent polygons.


Discard:Use this option to discard extra data points in the output geometry.